Information processing device that displays a virtual object relative to real space

ABSTRACT

An information processing device including a display unit, a detector, and a first control unit and a method of using same. The display unit may be a head-mounted display. The display unit is capable of providing the user with a field of view of a real space and a virtual object. The detector detects an azimuth of the display unit around at least one axis and display of the virtual object is controlled based in the detected azimuth.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/968,035 filed Oct. 18, 2022, which is a continuation of U.S. patentapplication Ser. No. 16/700,211 filed Dec. 2, 2019, now U.S. Pat. No.11,513,353 issued Nov. 29, 2022, which is a continuation of U.S. patentapplication Ser. No. 16/392,859 filed Apr. 24, 2019, now U.S. Pat. No.10,534,183 issued Jan. 14, 2020, which is a continuation of U.S. patentapplication Ser. No. 15/860,779 filed Jan. 3, 2018, now U.S. Pat. No.10,317,681 issued Jun. 11, 2019, which is a continuation of U.S. patentapplication Ser. No. 14/394,222 filed Oct. 13, 2014, now U.S. Pat. No.9,910,281 issued Mar. 6, 2018, which is a National Stage PatentApplication of PCT International Patent Application No.PCT/JP2014/000957 filed Feb. 24, 2014, which claims priority to JapanesePatent Application No. 2013-033076 filed Feb. 22, 2013, which are allhereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a head-mounted display that is capableof displaying an image including particular information in a displayfield-of-view.

BACKGROUND ART

There is known a technique of adding a corresponding image to the realspace, which is called augmented reality (AR). For example, PatentDocument 1 describes a virtual image stereoscopic synthesis devicecapable of displaying three-dimensional shape information of anarbitrary object in a real space to which an observer belongs. Further,Patent Document 2 describes a head-mounted display capable of displayingan object relating to a target present in an external world viewed by auser.

-   Patent Document 1: Japanese Patent Application Laid-open No.    2000-184398-   Patent Document 2: Japanese Patent Application Laid-open No.    2012-053643

SUMMARY OF INVENTION Problem to be Solved by the Invention

In recent years, in a see-through-type head-mounted display, forexample, there is a case where it is desirable to limit an informationdisplay area while ensuring a see-through area. In this case, there is afear that it is difficult for an object to enter a field of view of adisplay or it is difficult to keep a state in which the object is in thefield of view.

In view of the above-mentioned circumstances, it is an object of thepresent technology to provide a head-mounted display that is capable ofenhancing the searchability or visibility of an object.

Means for Solving the Problem

A head-mounted display according to an embodiment of the presenttechnology includes a display unit, a detector, and a first controlunit.

The display unit is mountable on a head of a user and configured to becapable of providing the user with a field of view of a real space.

The detector detects an azimuth of the display unit around at least oneaxis.

The first control unit includes a region limiter, a storage unit, and adisplay control unit. The region limiter is configured to be capable oflimiting a display region of the field of view along a direction of theone axis in three-dimensional coordinates surrounding the display unit.The storage unit stores images including information relating to apredetermined target present in the field of view with the images beingmade corresponding to the three-dimensional coordinates. The displaycontrol unit is configured to display, based on an output of thedetector, an image in the three-dimensional coordinates, whichcorresponds to the azimuth, in the field of view.

According to the head-mounted display, the probability that the imagedisplayed in accordance with a change in attitude around the one axisenters the field of view of the user is higher, and hence it is possibleto enhance the searchability of the image. Further, it is possible toeasily keep the state in which the image is in the field of view, andhence it is also possible to enhance the visibility of the image.

The “azimuth of the display unit” typically means a front direction ofthe display unit. Regarding the head-mounted display, the frontdirection of the display unit can be defined as a front direction of theuser. Thus, the “azimuth of the display unit” can be interpreted asbeing the same as a direction of the face of the user.

The “azimuth of the display unit around the one axis” means an azimuthof the display unit with the one axis being a center. For example, inthe case where the one axis is a vertical axis, horizontal directions ofthe east, west, south, and north correspond to it. In this case, forexample, if the north is set as a reference azimuth, an angle from thisazimuth can indicate the azimuth of the display unit. On the other hand,if the one axis is a horizontal axis, the azimuth of the display unitaround the one axis can be indicated by an angle of elevation or anangle of depression with a horizontal plane being a reference. The oneaxis is not limited to such examples. The one axis may be another axisintersecting the vertical axis and the horizontal axis.

The display control unit may be configured to acquire information on arelative position between the display unit and the predetermined targetand control a display mode of an image displayed in the field of view inaccordance with a change in relative position. With this, it is possibleto keep or enhance the visibility of the image displayed in the field ofview.

The information on the relative position may include information on arelative distance between the display unit and the predetermined target.In this case, the display control unit may be configured to change, inaccordance with the change in relative distance, at least one of aposition and a size of the image displayed in the field of view.

Alternatively, the information on the relative position may includeinformation on an angular position of the display unit with thepredetermined target being a center. In this case, the display controlunit may be configured to three-dimensionally change, in accordance witha change in angular position, an orientation of the image displayed inthe field of view.

The display control unit may be configured to extract an image includinginformation meeting at least one display condition set by the user fromthe storage unit and selectively display the extracted image in thefield of view. With this, it is possible to display only informationsignificant for the user in the field of view.

The display control unit may be configured to alternately display, whenan image that should be displayed in the field of view includes aplurality of images, each of the plurality of images. With this, it ispossible to increase the discriminability of the individual imagesdisplayed in the field of view.

The storage unit may store a plurality of images relating to thepredetermined target. In this case, the display control unit may beconfigured to select, according to a user operation, an image thatshould be displayed in the field of view from among the plurality ofimages. With this, it is possible to individually display the pluralityof images including information on the same target.

The detector may detect an azimuth of the display unit around a verticalaxis, and the region limiter may limit a region in a height direction incylindrical coordinates around the vertical axis in accordance with aregion of the field of view in a vertical direction. With this, it ispossible to enhance the searchability and visibility of the image in thehorizontal field of view of the user.

The display control unit may move, when the azimuth is changed by afirst predetermined angle or larger, the image in the field of view inaccordance with a change in azimuth, and fix a display position of theimage in the field of view when the change in azimuth is smaller thanthe first predetermined angle. With this, it is possible to regulate themovement of the image, which results from an intended change in attitudeof the user around the vertical axis and to enhance the visibility ofthe image.

The detector may be configured to further detect a change in attitude ofthe display unit around a horizontal axis. In this case, the displaycontrol unit moves, when the change in attitude is equal to or largerthan a second predetermined angle, the image in the field of view inaccordance with the change in attitude, and fixes, when the change inattitude is smaller than the second predetermined angle, the displayposition of the image in the field of view. With this, it is possible toregulate the movement of the image, which results from an unintendedchange in attitude of the user around the horizontal axis, and tofurther enhance the visibility of the image.

The display control unit may move the image to a predetermined positionin the field of view when a change in output of the detector is equal toor smaller than a predetermined value over a predetermined time. Thatis, if the output of the detector is not changed over a predeterminedtime, the probability that the user is referring to the image displayedin the field of view is high, and hence the visibility of the image isincreased by moving the image to the predetermined position in the fieldof view. The predetermined position may be, for example, the center ofthe field of view. In addition, the image after movement may bedisplayed in an enlarged state.

The display control unit may move the image to a predetermined positionin the field of view when an input of a predetermined signal generatedaccording to an operation of the user is detected. Also with thisconfiguration, it is possible to increase the visibility of the image asdescribed above and to control the display of the image according to theintention of the user.

The display control unit may cancel, when a change in output of thedetector is equal to or higher than a predetermined frequency in a statein which the image is displayed at a predetermined position in the fieldof view, a frequency component of the output of the detector, which isequal to or higher than the predetermined frequency. For example, thepredetermined frequency is set to a frequency corresponding to a shakeof the face of the user. With this, it is possible to ensure thevisibility of the image without receiving the influence of the slightshake of the face of the user.

The first control unit may be configured to limit, when an input of apredetermined signal generated according to an operation of the user isdetected, a region in the height direction in the three-dimensionalcoordinates in accordance with a region of the field of view in thedirection of the one axis, and adjust all the images displayed in thefield of view to the same height in the field of view. With this, it ispossible to further enhance the visibility of the image displayed in thefield of view.

The image can include information relating to a predetermined targetpresent in the field of view. With this, it is possible to provideinformation relating to the target to the user. Further, the image maybe a still image or may be a moving image such as an animation image.

The detector is not particularly limited as long as it can detect achange in azimuth or attitude of the display unit. For example, aterrestrial magnetism sensor, a motion sensor, a combination thereof, orthe like can be employed.

The head-mounted display may further include a second control unitincluding an image acquisition unit that acquires a plurality of imagesstored in the storage unit.

The first control unit may be configured to request the second controlunit to transmit one or more images selected from among the plurality ofimages. Necessary images can be acquired mainly by the first controlunit in a necessary order in this manner, and hence it is possible toconstruct a system that overcomes problems of communication speedbetween the first and second control units, a time from issue of thetransmission request to actual transmission of the image (latency), andthe like.

In this case, the first control unit may be configured to request thesecond control unit to preferentially transmit an image madecorresponding to a coordinate position closer to the display region ofthe field of view in the three-dimensional coordinates.

Note that, in the case where the image is an animation image, prioritysetting only needs to be performed in view of a current time and ananimation frame time. For example, the first control unit may beconfigured to request the second control unit to collectively transmitat least some of all images constituting the animation image.

The first control unit may be configured to regularly evaluate, withrespect to all the images stored in the storage unit, a distance betweenthe coordinate position and the display region of the field of view andremove an image at a coordinate position furthest from the displayregion of the field of view from the storage unit. With this, it ispossible to reduce the capacity of the storage unit.

The second control unit may further include a position informationacquisition unit that is capable of acquiring position information ofthe display unit. The image acquisition unit acquires an imagecorresponding to the position information that can be transmitted to thefirst control unit. With this, the second control unit can acquire anoptimal image in accordance with a current position of the user.

A head-mounted display according to another embodiment of the presenttechnology includes a display unit, a detector, and a control unit.

The display unit is mountable on a head of a user and configured to becapable of providing the user with a field of view of a real space.

The detector detects an azimuth of the display unit around at least oneaxis.

The control unit includes a storage unit and display control unit. Thestorage unit stores images including information relating to apredetermined target present in the field of view with the images beingmade corresponding to three-dimensional coordinates surrounding thedisplay unit. The display control unit is configured to display, basedon an output of the detector, an image in the three-dimensionalcoordinates, which corresponds to the azimuth, in the field of view.

The display control unit may be configured to convert a predeterminedimage stored in the storage unit into a coordinate value falling withina display area of the field of view along a direction of the one axisand display it in the field of view. With this, it is possible toincrease the searchability of the image made corresponding to eachazimuth.

Effect of the Invention

As described above, according to the present technology, it is possibleto enhance the searchability or visibility of an object image.

Note that the effects described herein are not necessarily limited andmay be any of the effects described in the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A schematic view for describing functions of a head-mounteddisplay according to an embodiment of the present technology.

FIG. 2 A general view showing the head-mounted display.

FIG. 3 A block diagram showing a configuration of a system including thehead-mounted display.

FIG. 4 A function block diagram of a control unit in the head-mounteddisplay.

FIG. 5A A schematic view showing cylindrical coordinates as an exampleof a world coordinate system in the head-mounted display.

FIG. 5B A schematic view showing cylindrical coordinates as an exampleof the world coordinate system in the head-mounted display.

FIG. 6A A development view of the cylindrical coordinates shown in FIG.5A.

FIG. 6B A development view of the cylindrical coordinates shown in FIG.5B.

FIG. 7 An explanatory view of a coordinate position in the cylindricalcoordinate system.

FIG. 8 A development view of the cylindrical coordinates conceptuallyshowing a relationship between a field of view and objects.

FIG. 9A A view for describing a method of converting cylindricalcoordinates (world coordinates) into a field of view (localcoordinates).

FIG. 9B A view for describing a method of converting cylindricalcoordinates (world coordinates) into a field of view (localcoordinates).

FIG. 10A A conceptual diagram for describing an image stabilizationfunction in the head-mounted display.

FIG. 10B A conceptual diagram for describing the image stabilizationfunction in the head-mounted display.

FIG. 11A A schematic view showing a relative position relationshipbetween objects made corresponding to cylindrical coordinates whoseregion is limited and the field of view.

FIG. 11B A schematic view showing a relative position relationshipbetween objects made corresponding to the cylindrical coordinates whoseregion is limited and the field of view.

FIG. 12A A conceptual diagram for describing a procedure of arrangingobjects in the cylindrical coordinates whose region is limited.

FIG. 12B A conceptual diagram for describing a procedure of arrangingobjects in the cylindrical coordinates whose region is limited.

FIG. 13 A sequence diagram for describing a procedure of arranging theobjects in the cylindrical coordinates whose region is limited.

FIG. 14 A flowchart for describing an outline of operations of thesystem.

FIG. 15 A flowchart showing an example of a procedure of receivingobject data items by the control unit.

FIG. 16 A flowchart showing an example of a procedure of drawing theobjects in the field of view by the control unit.

FIG. 17 A schematic view of a field of view for describing anapplication example in the head-mounted display.

FIG. 18 A schematic view of a field of view for describing theapplication example in the head-mounted display.

FIG. 19 A schematic view of a field of view for describing theapplication example in the head-mounted display.

FIG. 20 A schematic view of a field of view for describing theapplication example in the head-mounted display.

FIG. 21 A schematic view of a field of view for describing theapplication example in the head-mounted display.

FIG. 22 A schematic view of a field of view for describing theapplication example in the head-mounted display.

FIG. 23 A flowchart showing a display control example in thehead-mounted display.

FIG. 24 A schematic view of a field of view for describing the displaycontrol example.

FIG. 25A A schematic view of a field of view for describing anotherdisplay control example.

FIG. 25B A schematic view of a field of view for describing the otherdisplay control example.

FIG. 26 A schematic view for describing an action of the head-mounteddisplay according to another embodiment of the present technology.

FIG. 27A A schematic view for describing an action of the head-mounteddisplay.

FIG. 27B A schematic view for describing an action of the head-mounteddisplay.

FIG. 27C A schematic view for describing an action of the head-mounteddisplay.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments according to the present technology will bedescribed with reference to the drawings. In this embodiment, an examplein which the present technology is applied to a head-mounted display asan image display apparatus will be described.

First Embodiment

FIG. 1 is a schematic view for describing functions of a head-mounteddisplay (hereinafter, referred to as HMD) according to an embodiment ofthe present technology. First, referring to FIG. 1 , an outline of basicfunctions of the HMD according to this embodiment will be described.

In FIG. 1 , an X-axis direction and a Y-axis direction show horizontaldirections orthogonal to each other and a Z-axis direction shows avertical axis direction. Such an XYZ orthogonal coordinate systemexpresses a coordinate system of a real space (real three-dimensionalcoordinate system) to which a user belongs. An X-axis arrow indicates anorth direction and a Y-axis arrow indicates an east direction. Further,a Z-axis arrow indicates a gravity direction.

[Outline of Functions of HMD]

An HMD 100 according to this embodiment is mounted on the head of a userU and configured to be capable of displaying a virtual image in a fieldof view V (display field-of-view) of a real space of the user U. Theimage displayed in the field of view V includes information relating topredetermined targets A1, A2, A3, and A4 present in the field of view V.The predetermined targets are, for example, landscape, shops, or goodssurrounding the user U.

The HMD 100 stores images (hereinafter, referred to as objects) B1, B2,B3, and B4 made corresponding to a virtual world coordinate systemsurrounding the user U who wears the HMD. The world coordinate system isa coordinate system equivalent to the real space to which the userbelongs. In the world coordinate system, the targets A1 to A4 arepositioned with the position of the user U and a predetermined axisdirection being references. Although cylindrical coordinates C0 with thevertical axis being a center of axis are employed as the worldcoordinates in this embodiment, other three-dimensional coordinates suchas celestial coordinates with the user U being a center may be employed.

A radius R and a height H of the cylindrical coordinates C0 can bearbitrarily set. Although the radius R is set to be shorter than adistance from the user U to the targets A1 to A4 here, the radius R maybe longer than the distance. Further, the height H is set to be equal toor larger than a height (vertical length) Hv of the field of view V ofthe user U, which is provided through the HMD 100.

The objects B1 to B4 are images showing information relating to thetargets A1 to A4 present in the world coordinate system. The objects B1to B4 may be images including letters, patterns, and the like or may beanimation images. Alternatively, the objects may be two-dimensionalimages or may be three-dimensional images. In addition, the object shapemay be a rectangular shape, a circular shape, or another geometric shapeand can be appropriately set depending on the kind of object.

Coordinate positions of the objects B1 to B4 in the cylindricalcoordinates C0 are, for example, made corresponding to intersectionpositions of lines of sight L of the user who gazes at the targets A1 toA4 and the cylindrical coordinates C0. Although center positions of theobjects B1 to B4 are made coincide with the intersection positions inthe illustrated example, it is not limited thereto and part ofperipheries (e.g., part of four corners) of the objects may be madecoincide with the intersection positions. Alternatively, the coordinatepositions of the objects B1 to B4 may be made corresponding to anypositions spaced apart from the intersection positions.

The cylindrical coordinates C0 have a coordinate axis (θ) in acircumferential direction that expresses an angle around the verticalaxis with the north direction being 0° and a coordinate axis (h) in aheight direction that expresses an angle in upper and lower directionswith a horizontal line of sight Lh of the user U being a reference. Thecoordinate axis (θ) has a positive direction from the west to the east.The coordinate axis (h) uses the angle of depression as a positivedirection and the angle of elevation as a negative direction.

As will be described later, the HMD 100 includes a detector fordetecting a direction of the eyes of the user U and determines, based onthe output of the detector, which region in the cylindrical coordinatesC0 the field of view V of the user U corresponds to. If any object(e.g., object B1) is present in the corresponding region of anxy-coordinate system, which forms the field of view V, the HMD 100displays (draws) the object B1 in the corresponding region.

As described above, the HMD 100 according to this embodiment displaysthe object B1 in the field of view V while being overlapped with thetarget A1 in the real space, to thereby provide the user U withinformation relating to the target A1. Further, the HMD 100 can providethe objects (B1 to B4) relating to the predetermined targets A1 to A4 tothe user U in accordance with the azimuth or direction of the eyes ofthe user U.

Next, the HMD 100 will be described in detail. FIG. 2 is a general viewshowing the HMD 100 and FIG. 3 is a block diagram showing aconfiguration thereof.

[Configuration of HMD]

The HMD 100 includes a display unit 10, a detector 20 that detects anattitude of the display unit 10, and a control unit 30 that controlsdriving of the display unit 10. In this embodiment, the HMD 100 isconstituted of a see-through-type HMD capable of providing the user withthe field of view V of the real space.

(Display Unit)

The display unit 10 is configured to be mountable on the head of theuser U. The display unit 10 includes first and second display surfaces11R and 11L, first and second image generators 12R and 12L, and asupport 13.

The first and second display surfaces 11R and 11L are constituted ofoptical elements having transparency that can provide the right eye andleft eye of the user U with the real space (external field of view). Thefirst and second image generators 12R and 12L are configured to becapable of generating images to be presented to the user U via the firstand second display surfaces 11R and 11L. The support 13 supports thedisplay surfaces 11R and 11L and the image generators 12R and 12L. Thefirst and second display surfaces 11L and 11R have a suitable shape suchthat they are mountable on the head of the user to be opposed to theright eye and left eye of the user U, respectively.

The thus configured display unit 10 is configured to be capable ofproviding the user U with the field of view V with predetermined images(or virtual images) being overlapped with the real space, through thedisplay surfaces 11R and 11L. In this case, cylindrical coordinates C0for the right eye and cylindrical coordinates C0 for the left eye areset and an object drawn in each of the cylindrical coordinates isprojected to the display surfaces 11R and 11L.

(Detector)

The detector 20 is configured to be capable of detecting a change inazimuth or attitude of the display unit 10 around at least one axis. Inthis embodiment, the detector 20 is configured to detect changes inazimuth or attitude of the display unit 10 around the X-, Y-, andZ-axes.

The azimuth of the display unit 10 typically means a front direction ofthe display unit. In this embodiment, the azimuth of the display unit 10is defined as a face direction of the user U.

The detector 20 can be constituted of a motion sensor such as an angularvelocity sensor and an acceleration sensor or a combination thereof. Inthis case, the detector 20 may be constituted of a sensor unit in whichthe angular velocity sensor and the acceleration sensor are arranged inthree axis directions or a different sensor may be used for each axis.For example, an integrated value of the output of the angular velocitysensor can be used for a change in attitude of the display unit 10, adirection of the change, the amount of change thereof, or the like.

Further, a terrestrial magnetism sensor may be employed for detectingthe azimuth of the display unit 10 around the vertical axis (Z-axis).

Alternatively, the terrestrial magnetism sensor and the motion sensormay be combined. With this, it becomes possible to detect a change inazimuth or attitude with a high accuracy.

The detector 20 is located at an appropriate position in the displayunit 10. The position of the detector 20 is not particularly limited.For example, the detector 20 is located on either one of the imagegenerators 12R and 12L or part of the support 13.

(Control Unit)

The control unit 30 (first control unit) generates, based on the outputof the detector 20, a control signal for controlling driving of thedisplay unit 10 (image generators 12R and 12L). In this embodiment, thecontrol unit 30 is electrically connected to the display unit 10 via aconnection cable 30 a. Of course, the control unit 30 is not limitedthereto. The control unit 30 may be connected to the display unit 10 bywireless communication.

As shown in FIG. 3 , the control unit 30 includes a CPU 301, a memory302 (storage unit), a transmitter/receiver 303, an internal power source304, and an input operation unit 305.

The CPU 301 controls an operation of the entire HMD 100. The memory 302includes a read only memory (ROM), a random access memory (RAM), and thelike and stores programs and various parameters for controlling the HMD100 by the CPU 301, images (objects) that should be displayed on thedisplay unit 10, and other necessary data. The transmitter/receiver 303constitutes an interface for communication with a portable informationterminal 200, which will be described later. The internal power source304 supplies a power necessary for driving the HMD 100.

The input operation unit 305 serves to control images displayed on thedisplay unit 10 according to a user operation. The input operation unit305 may be constituted of a mechanical switch or may be constituted of atouch sensor. The input operation unit 305 may be provided in thedisplay unit 10.

The HMD 100 may further include an audio output unit such as a speaker,a camera, and the like. In this case, the audio output unit and thecamera are typically provided in the display unit 10. In addition, thecontrol unit 30 may be provided with a display device that displays aninput operation screen or the like of the display unit 10. In this case,the input operation unit 305 may be constituted of a touch panelprovided in the display device.

(Portable Information Terminal)

The portable information terminal 200 (second control unit) isconfigured to be mutually communicable with the control unit 30 bywireless communication. The portable information terminal 200 functionsto acquire an image, which should be displayed in the display unit 10,and transmit an acquired image to the control unit 30. The portableinformation terminal 200 constructs an HMD system by being organicallycombined with the HMD 100.

Although the portable information terminal 200 is carried by the user Uwho wears the display unit 10 and constituted of an informationprocessing apparatus such as a personal computer (PC), a smartphone, acellular phone, a tablet PC, and a personal digital assistant (PDA), theportable information terminal 200 may be a terminal apparatus dedicatedto the HMD 100.

As shown in FIG. 3 , the portable information terminal 200 includes aCPU 201, a memory 202, a transmitter/receiver 203, an internal powersource 204, a display unit 205, a camera 206, and a position informationacquisition unit 207.

The CPU 201 controls the operation of the entire portable informationterminal 200. The memory 202 includes a ROM, a RAM, and the like andstores programs and various parameters for controlling the portableinformation terminal 200 by the CPU 201, an image (object) to betransmitted to the control unit 30, and other necessary data. Theinternal power source 204 supplies a power necessary for driving theportable information terminal 200.

The transmitter/receiver 203 communicates with a server N, the controlunit 30, and another adjacent portable information terminal or the like,using wireless LAN (IEEE802.11 or the like) such as wireless fidelity(WiFi) and a 3G or 4G network for portable communication. The portableinformation terminal 200 downloads, from the server N via thetransmitter/receiver 203, images (objects), which should be transmittedto the control unit 30, and applications for displaying them and storesthem in the memory 202.

The server N is typically constituted of a computer including a CPU, amemory, and the like and transmits predetermined information to theportable information terminal 200 in response to a request of the user Uor automatically irrespective of the intention of the user U.

The display unit 205 is constituted of, for example, LCD or OLED anddisplays various menus, GUIs of applications, or the like. Typically,the display unit 205 is integrated with a touch panel and can receive atouch operation of the user. The portable information terminal 200 canbe configured to be capable of inputting a predetermined operationsignal to the control unit 30 by a touch operation of the display unit205.

The position information acquisition unit 207 typically includes aglobal positioning system (GPS) receiver. The portable informationterminal 200 is configured to be capable of measuring a current position(longitude, latitude, altitude) of the user U (display unit 10) usingthe position information acquisition unit 207 and acquiring images(objects) necessary from the server N. That is, the server N acquiresinformation on a current position of the user and transmits image data,application software, and the like corresponding to the positioninformation to the portable information terminal 200.

(Details of Control Unit)

Next, the control unit 30 will be described in details.

FIG. 4 is a function block diagram of the CPU 301. The CPU 301 includesa coordinate setting unit 311, an image management unit 312, acoordinate determination unit 313, and a display control unit 314. TheCPU 301 executes processes in the coordinate setting unit 311, the imagemanagement unit 312, the coordinate determination unit 313, and thedisplay control unit 314 according to the programs stored in the memory302.

The coordinate setting unit 311 is configured to execute a process ofsetting three-dimensional coordinates surrounding the user U (displayunit 10). In this example, the cylindrical coordinates C0 (see FIG. 1 )with a vertical axis Az being a center is used as the three-dimensionalcoordinates. The coordinate setting unit 311 sets the radius R and theheight H of the cylindrical coordinates C0. The coordinate setting unit311 typically sets the radius R and the height H of the cylindricalcoordinates C0 depending on the number and kinds of objects that shouldbe presented to the user U.

Although the radius R of the cylindrical coordinates C0 may be a fixedvalue, the radius R may be a variable value that can be arbitrarily setdepending on the size (pixel size) or the like of an image that shouldbe displayed. The height H of the cylindrical coordinates C0 is set to,for example, one to three times larger than a height Hv (see FIG. 1 ) ofthe field of view V in a vertical direction (perpendicular direction),which should be provided to the user U by the display unit 10. An upperlimit of the height H is not limited to be three times larger than Hvand may be three or more times larger than Hv.

FIG. 5A shows cylindrical coordinates C0 having a height H1 equal to theheight Hv of the field of view V. FIG. 5B shows cylindrical coordinatesC0 having a height H2 three times larger than the height Hv of the fieldof view V.

FIGS. 6A and 6B are schematic views showing cylindrical coordinates C0in a developed state. As described above, the cylindrical coordinates C0include a coordinate axis (θ) in the circumferential direction showingan angle around the vertical axis with the north direction being 0° anda coordinate axis (h) in the height direction showing an angle in theupper and lower directions with the horizontal line of sight Lh of theuser U being a reference. The coordinate axis (θ) has the positivedirection from the west to the east and the coordinate axis (h) uses theangle of depression as the positive direction and the angle of elevationas the negative direction. A height h indicates a magnitude when themagnitude of the height Hv of the field of view V is set to 1001. Anorigin OP1 of the cylindrical coordinates C0 is set to an intersectionpoint of an azimuth (0°) in the north direction and a horizontal line ofsight Lh (h=0%) of the user U.

The coordinate setting unit 311 functions as a region limiter capable oflimiting a display region of the field of view V along a direction ofthe one axis in the three-dimensional coordinates surrounding thedisplay unit 10. In this embodiment, the coordinate setting unit 311limits a field-of-view region (Hv) of the field of view V in the heightdirection in the cylindrical coordinates C0 surrounding the display unit10. Specifically, the coordinate setting unit 311 limits, when thespecified value of the height (H) is larger than the height Hv of thefield of view V, the height (H) of the cylindrical coordinates in aregion of the field of view V in the height direction. In addition, thecoordinate setting unit 311 limits, for example, the height of thecylindrical coordinates from H2 (FIG. 5B) to H1 (FIG. 5A) according toan operation of the user U.

The image management unit 312 functions to manage images stored in thememory 302. For example, the image management unit 312 is configured toexecute a process of storing one or more images, which are displayed viathe display unit 10, in the memory 302, and selectively removing theimages stored in the memory 302. The images stored in the memory 302 aretransmitted from the portable information terminal 200. The imagemanagement unit 312 also requests the portable information terminal 200to transmit an image via the transmitter/receiver 303.

The memory 302 is configured to be capable of storing one or more images(objects), which should be displayed in the field of view V, with theone or more images (objects) being made corresponding to the cylindricalcoordinates C0. That is, the memory 302 stores the respective objects B1to B4 in the cylindrical coordinates C0 shown in FIG. 1 together withthe coordinate positions in the cylindrical coordinates C0.

As shown in FIG. 7 , a cylindrical coordinate system (θ, h) and anorthogonal coordinate system (X, Y, Z) have a relationship amongX=rcosθ, Y=rsinθ, and Z=h. As shown in FIG. 1 , the objects B1 to B4that should be displayed corresponding to the azimuth or the attitude ofthe field of view V occupy specific coordinate regions in thecylindrical coordinates C0 and are stored in the memory 302 togetherwith particular coordinate positions P(θ, h) in the region.

The coordinates (θ, h) of the objects B1 to B4 in the cylindricalcoordinates C0 are made corresponding to coordinates of a cylindricalcoordinate system at an intersection of a straight line linking thepositions of the targets A1 to A4 each defined by an orthogonal system(X, Y, Z) and the position of the user and a cylindrical surface of thecylindrical coordinates C0. That is, the coordinates of the objects B1to B4 correspond to coordinates of the targets A1 to A4 converted fromreal three-dimensional coordinates into the cylindrical coordinates C0.Such coordinate conversion of the objects is, for example, executed atthe image management unit 312 and the objects are stored in the memory302 together with coordinate positions thereof. The cylindricalcoordinates C0 are employed in the world coordinate system, and hence itis possible to draw the objects B1 to B4 in a planar manner.

The coordinate positions of the objects B1 to B4 may be set at anypositions as long as they are within the display region of each of theobjects B1 to B4. A particular point (e.g., center position) or two ormore points (e.g., two diagonal points or four corner points) may be setper an object.

Further, as shown in FIG. 1 , when the coordinate positions of theobjects B1 to B4 are made corresponding to intersection positions of theline of sight L of the user who gazes at the targets A1 to A4 and thecylindrical coordinates C0, the user U views the objects B1 to B4 atpositions overlapping with the targets A1 to A4. Instead of this, thecoordinate positions of the objects B1 to B4 may be made correspondingto any positions spaced apart from the intersection positions. Withthis, the objects B1 to B4 can be displayed or drawn at desiredpositions with respect to the targets A1 to A4.

The coordinate determination unit 313 is configured to execute a processof determining, based on the output of the detector 20, which region inthe cylindrical coordinates C0 the field of view V of the user Ucorresponds to. That is, the field of view V is moved in the cylindricalcoordinates C0 due to a change in attitude of the user U (display unit10) and the movement direction and the amount of movement are calculatedbased on the output of the detector 20. The coordinate determinationunit 313 calculates the movement direction and the amount of movement ofthe display unit 10 based on the output of the detector 20 anddetermines which region in the cylindrical coordinates C0 the field ofview V belongs to.

FIG. 8 is a development view of the cylindrical coordinates C0conceptually showing a relationship between the field of view V in thecylindrical coordinates C0 and the objects B1 to B4. The field of view Vis almost rectangular and includes xy-coordinates (local coordinates)with an upper left corner being an origin point OP2. The x-axis is anaxis extending from the origin point OP2 in the horizontal direction andthe y-axis is an axis extending from the origin point OP2 in theperpendicular direction. Then, the coordinate determination unit 313 isconfigured to execute a process of determining whether or not any of theobjects B1 to B4 is present in the corresponding region of the field ofview V.

The display control unit 314 is configured to execute a process ofdisplaying (drawing) an object in the cylindrical coordinates C0, whichcorresponds to the azimuth of the display unit 10, in the field of viewV based on the output of the detector 20 (i.e., determination result ofcoordinate determination unit 313). For example, as shown in FIG. 8 ,when a current azimuth of the field of view V overlaps with each of thedisplay regions of the objects B1 and B2 in the cylindrical coordinatesC0, images corresponding to overlapping regions B10 and B20 thereof aredisplayed in the field of view V (local rendering).

FIGS. 9A and 9B are views for describing a method of converting thecylindrical coordinates C0 (world coordinates) into the field of view V(local coordinates).

As shown in FIG. 9A, it is assumed that coordinates of a reference pointof the field of view V in the cylindrical coordinates C0 are denoted by(θv, hv) and coordinates of a reference point of an object B located ina region of the field of view V are denoted by (θ0, h0). The referencepoints of the field of view V and the object B may be set to any points.In this example, the reference points are set to upper left corners ofthe field of view V and the object B each of which has a rectangularshape. αv[° ] is a width angle of the field of view V in the worldcoordinates and the value is determined depending on the design orspecification of the display unit 10.

The display control unit 314 converts the cylindrical coordinate system(θ, h) into a local coordinate system (x, y), to thereby determine adisplay position of the object B in the field of view V. As shown inFIG. 9B, assuming that the height and width of the field of view V inthe local coordinate system are denoted by Hv and Wv respectively andthe coordinates of the reference point of the object B in the localcoordinate system (x, y) are denoted by (x0, y0), the conversionexpression is as follows.

x0=(θ0-θv)*Wv/αv  (1)

y0=(h0-hv)+Hv/100  (2)

The display control unit 314 typically changes the display position ofthe object B in the field of view V following the change in azimuth orattitude of the display unit 10. This control is continued as long as atleast part of the object B is present in the field of view V.

However, the display region tends to be narrower due to downsizing ofthe HMD in recent years. Further, in the see-through-type head-mounteddisplay, there is, for example, a case where it is desirable to limitthe information display region while ensuring the see-through region. Insuch a case, when the display position of the object B is changed in thefield of view V following the change in azimuth or attitude of thedisplay unit 10 as described above, there is a fear that it becomesdifficult to keep the object B in the field of view V. In order to solvesuch a problem, the HMD 100 according to this embodiment has an objectdisplay fixing function as described below.

<Object Display Fixing Function>

(1) Introduction of Non Strict Attribute

The display control unit 314 is configured to be capable of executing aprocess of moving the object in the field of view V in accordance withthe change in azimuth or attitude when the azimuth or the attitude ofthe display unit 10 is changed by a predetermined angle or larger, andfixing the display position of the object in the field of view V whenthe change in azimuth or attitude is smaller than the predeterminedangle.

In this embodiment, a non-strict attribute may be introduced into theobject. That is, if the object B is not fixed at one position of theworld coordinate system (cylindrical coordinates C0) and the directionof the eyes of the user U falls within a certain angle range, the objectmay be fixed and displayed at the local coordinate system (x, y) of thedisplay unit 10. By executing such a process, it is possible to easilykeep the state in which the object is in the field of view V. Thus, themovement of the object due to an unintended change in attitude of theuser U around the vertical axis or the horizontal axis is regulated, andthe visibility of the object can be increased.

The predetermined angle may be an angle around the vertical axis(Z-axis), may be an angle around the horizontal axis (X-axis and/orY-axis), or may be both of them. The value of the predetermined anglecan be appropriately set and is, for example, ±15°. The predeterminedangle may be the same between an angle (first predetermined angle)around the vertical axis and an angle (second predetermined angle)around the horizontal axis or may be different therebetween.

(2) First Grab Function

The display control unit 314 is configured to be capable of executing aprocess of moving the object B to a predetermined position in the fieldof view V when a change in output of the detector 20 is equal to orsmaller than a predetermined value over a predetermined time.

In this embodiment, if the output of the detector 20 is not changed overa predetermined time, the probability that the user is referring to theobject displayed in the field of view V is high, and hence thevisibility of the object may be increased by moving the object to apredetermined position in the field of view V.

The predetermined time is not particularly limited and is, for example,set to about five seconds. Further, the predetermined position is notparticularly limited and is, for example, the center or corner of thefield of view V or a deviated position that is any one of the upper,lower, left, and right positions. In addition, the object after movementmay be displayed in an exaggeration state, for example, an enlargedstate.

For example, if a change in output of the detector 20 is not recognizedfor a predetermined time with the object being at the center of thefield of view V, this function may fixedly display the object B at apredetermined position of the local coordinate system (x, y) of thefield of view V. In this case, when the output of the detector 20exceeds a predetermined value, the function of fixedly displaying theobject is released. The output value of the detector 20 at this time maybe an amount of change in output that corresponds to a change inattitude that is equal to or larger than the predetermined angle of thedisplay unit 10 around the predetermined axis or may be another amountof change in output.

(3) Second Grab Function

When an input of a predetermined signal generated according to anoperation of the user U is detected, the display control unit 314 isconfigured to be capable of executing a process of moving the object toa predetermined position in the field of view V. Also with such aconfiguration, the visibility of the object can be increased asdescribed above and to control the display of the image in accordancewith the intention of the user.

In this process, for example, by adjusting the object to the center ofthe field of view V and performing a predetermined input operation onthe input operation unit 305 or the portable information terminal 200,the object is fixed to the local coordinate system (x, y) of the fieldof view V. Then, by operating the input operation unit 305 or the likeagain, the object is restored to the world coordinate system and thefunction of fixedly displaying the object is released.

(4) Image Stabilization Function

When a change in output of the detector 20 is equal or higher than apredetermined frequency with the object being displayed at apredetermined position in the field of view V, the display control unit314 is configured to be capable of executing a process of cancelingfrequency components of the output of the detector 20, which are equalto or higher than the predetermined frequency.

When the object in the field of view V is moved following a change inazimuth or attitude of the display unit 10, there is a fear that it alsofollows a slight shake of the face of the user U and the visibility ofthe object is deteriorated. In order to prevent this problem, the objectmay be prevented from following the change in attitude of the displayunit 10 for high frequency components equal to or higher than apredetermined value and the object-displaying position may be fixed inthe field of view V (local coordinate system) for low frequencycomponents lower than the predetermined value. For example, thepredetermined frequency is set to a frequency corresponding to the shakeof the face of the user. With this, it is possible to ensure thevisibility of the image without receiving the influence of the slightshake of the face of the user.

FIGS. 10A and 10B are conceptual diagrams for describing the imagestabilization function. In the figures, V1 denotes a local coordinatesystem at a certain point of time and V2 denotes an image stabilizationcoordinate system corresponding to V1. OP and OP′ show origins of V1 andV2.

When the image stabilization function is enabled, the object is placedin the image stabilization coordinate system. The image stabilizationcoordinate system is subjected to follow-up control with respect to thelocal coordinate system (x, y) of the field of view V by PD control. ThePD control is one of kinds of feed back control and generally refers toa control of converging to a setting value by combining a proportionalcontrol and a differential control. In FIGS. 10A and 10B, regarding aspring (p) and a damper (d) each connected between the field of view Vand a field of view V′, the spring (p) corresponds to a P component ofthe PD control and the damper (d) corresponds to a D component of the PDcontrol.

As an example of a method of calculating the follow-up control, it isassumed that a point in the local coordinate system V1 at a certainpoint t is denoted by (x(t), y(t)) and a point in the imagestabilization coordinate system V2 corresponding thereto is denoted by(x′ (t), y′ (t)). In addition, a point of a local coordinate system V1before a sampling period (Δt) is denoted by (x(t−Δt), y(t−Δt)) and apoint of an image stabilization coordinate system V2 correspondingthereto is denoted by (x′ (t−Δt), y′ (t−Δt)). Assuming that a differencebetween corresponding points is denoted by (Δx(t), Δy(t)), it isexpressed as follows.

Δx(t)=x′(t)−x(t)  (3)

Δy(t)=y′(t)−y(t)  (4)

Assuming that a speed difference between corresponding points is denotedby (Δvx(t), Δvy(t)), it is expressed as follows.

Δvx(t)={Δx′(t)−Δx′(t−Δt)}−{Δx(t)−Δx(t−Δt)}   (5)

Δvy(t)={Δy′(t)−Δy′(t−Δt))−{Δy(t)−Δy(t−Δt)}   (6).

An amount (Δp(t), Δq(t)) by which the image stabilization coordinatesystem V1′ should be moved following the local coordinate system V1 atthat time is expressed.

Δp(t)=Px×Δx(t)+Dx×Δvx(t)  (7)

Δq(t)=Py×Δy(t)+Dy×Δvy(t)  (8)

Where Px and Py are difference gain constants for x and y and Dx and Dyare speed gain constants for x and y.

Even if the local coordinate system V1 is rotated, the imagestabilization coordinate system V1′ does not follow a rotationalcomponent (FIG. 10B). That is, even if the user tilts the face around anaxis in front and back directions of the user, a tilt of the object isregulated.

The above-mentioned object display fixing functions (1) to (4) may beindividually applied or may be appropriately combined and applied. Forexample, a combination of any one of (1) to (3) above with (4) above isapplicable.

<Region-Limiting Function>

Next, a region-limiting function of the HMD 100 will be described.

In recent years, in a see-through-type head-mounted display, there is,for example, a case where it is desirable to limit an informationdisplay region while ensuring a see-through region. In this case, thereis a fear that it is difficult for the object image to enter the fieldof view. Therefore, in this embodiment, for the purpose of increasingthe searchability of the object, the region-limiting function of theworld coordinate system is provided.

As described above, the coordinate setting unit 311 functions as theregion limiter capable of limiting a region (H) along the Z-axisdirection in the cylindrical coordinates C0 surrounding the display unit10 in accordance with a region (Hv) in the height direction of the fieldof view V (see FIG. 5A). By limiting the height H of the cylindricalcoordinates C0, it is possible to increase the searchability and thevisibility of the image in a horizontal field of view of the user.

A limiting amount of the cylindrical coordinates C0 in the heightdirection is not particularly limited. In this embodiment, the height ofthe cylindrical coordinates C0 is limited to a height (H1) equal to theheight Hv of the field of view V. If the region-limiting function isenabled, the display control unit 314 is configured to be capable ofchanging at least the h coordinate of the cylindrical coordinate system(θ, h) and displaying the objects B1 to B4 in the field of view V suchthat the objects B1 to B4 are located in the cylindrical coordinates C0whose region is limited.

FIGS. 11A and 11B are schematic views showing a relative positionrelationship between the objects B1 to B4 made corresponding tocylindrical coordinates C1 whose region is limited to the height H1 andthe field of view V. The user U can view the objects B1 to B4 madecorresponding to all azimuths only by changing the attitude around theZ-axis (vertical axis), and hence the searchability of the objects B1 toB4 is dramatically increased.

Although all the objects B1 to B4 are located in the cylindricalcoordinates C1 in the example of FIG. 11A, it is not limited thereto,and at least an object may be located in the cylindrical coordinates C1depending on the needs. Further, the heights of the objects B1 to B4located in the cylindrical coordinates C1 are not particularly limitedand each of the heights can be appropriately set.

In addition, although the entire objects B1 to B4 are located in thecylindrical coordinates C1 in the example of FIG. 11 , at least part ofthe objects B1 to B4 may be displayed in the field of view V. With this,it is possible to easily recognize the image present at a certainazimuth. In this case, the height H1 of the cylindrical coordinates C1may be variable to a larger height according to an input operation bythe user U on the input operation unit 305 or the like. With this, theentire object can be viewed.

Whether to enable or disable the above-mentioned region-limitingfunction may be selectable according to settings by the user U. In theHMD 100 according to this embodiment, the region-limiting function usingthe world coordinate system as the cylindrical coordinates C1 is set inan enabled state as a normal mode. The change of the region-limitingfunction (e.g., change in height H) or switching to a disabled state canbe performed according to a spontaneous setting change by the user.

On the other hand, when detecting an input of a predetermined signalgenerated according to an operation of the user U, the control unit 30may be configured to be capable of executing a process of limiting aregion in the height direction in the cylindrical coordinates to theregion (Hv) in the height direction of the field of view V and aligningall the objects displayed in the field of view V at the same height inthe field of view V.

That is, if the region-limiting function is in an enabled state or ifthe world coordinate system is set in the cylindrical coordinates otherthan the cylindrical coordinates C1, the world coordinate system isforcedly switched to the cylindrical coordinates C1 according to aninput operation by the user U on the input operation unit 305 or thelike. In addition, the objects B1 to B4 are located at positions in thecylindrical coordinates C1 such that all the objects B1 to B4 aredisplayed at the same height in the field of view V as shown in FIG.11B. With this, it is possible to further enhance the visibility of theimage displayed in the field of view.

<Image Management Function>

Next, the image management function of the HMD 100 will be described.

As described above, in this embodiment, the portable informationterminal 200 is used for transmitting object data to the control unit30. The portable information terminal 200 includes the positioninformation acquisition unit 207 that measures a position of the user U(display unit 10) and an image acquisition unit including thetransmitter/receiver 203 or the like that is capable of acquiring theplurality of objects (B1 to B4), which should be stored in the memory302 of the control unit 30, from the server N or the like.

In this embodiment, the control unit 30 requests the portableinformation terminal 200 to transmit one or more object data itemsselected from among the plurality of object data items. Then, theportable information terminal 200 transmits the requested object data tothe control unit 30.

For smoothly drawing the objects in the field of view V of the displayunit 10, a communication speed between the portable information terminal200 and the control unit 30 and latency (time from issue of transmissionrequest to actual transmission of image) becomes problematic. In thisembodiment, for the purpose of αvoiding the problems of thecommunication speed and the latency, the control unit 30 (in thisexample, image management unit 312) is configured as follows.

First, the control unit 30 is configured to acquire a plurality ofobject data items necessary from the portable information terminal 200in advance. With this, the drawing timing of the objects in the field ofview V can be controlled at the control unit 30. It becomes possible toprovide the necessary objects to the user U at suitable timingirrespective of the communication environment and the like.

Further, the control unit 30 is configured to request the portableinformation terminal 200 to preferentially transmit the objects madecorresponding to coordinate positions closer to the display region ofthe field of view V in the cylindrical coordinates C0. By preferentiallyacquiring object data having high probability of being presented to thefield of view V in this manner, it is possible to αvoid the delay of theobject display in the field of view V.

At this time, the image management unit 312 is configured to be capableof executing a process of first setting one or more frames correspondingto arrangement positions of the objects in the world coordinates andthen arranging an object with a high priority in the frame. Note that“arrange the frame or object in the world coordinates” means making theframe or object corresponding to the world coordinates.

As an example, FIGS. 12A, 12B, and 13 show processes of arranging theobjects B3 and B4 in the cylindrical coordinates C1 whose region islimited to the height H1. Note that the following processes areapplicable also to cylindrical coordinates C0 whose region is notlimited or a world coordinate system constituted of otherthree-dimensional coordinates. In this embodiment, each of image dataitems of the objects (object data items) and the frame data items fordefining the coordinate positions of the objects is transmitted from theportable information terminal 200 to the control unit 30. The frame dataitems have an amount of data smaller than that of the object data items,and hence a necessary acquisition time thereof is shorter than that ofthe object data items. Therefore, a communication for frame dataacquisition is first performed and then a communication for object dataacquisition is performed in a priority order.

(Frame Registration Phase) First, the portable information terminal 200checks whether or not to transmit a frame F3 for arranging the object B3to the control unit 30 (Step 101). Correspondingly, the control unit 30requests the portable information terminal 200 to transmit the frame F3(Step 102). The control unit 30 stores the received frame F3 in thememory 302, to thereby arrange the frame F3 at the correspondingposition in the cylindrical coordinates C1.

Next, the portable information terminal 200 checks whether or not totransmit a frame F4 for arranging the object B4 to the control unit 30(Step 103). Correspondingly, the control unit 30 requests the portableinformation terminal 200 to transmit the frame F4 (Step 104). Thecontrol unit 30 stores the received frame F4 in the memory 302, tothereby arrange the frame F4 at the corresponding position in thecylindrical coordinates C1. After all frame data items are transmitted,the portable information terminal 200 notifies the control unit 30 of apermission to transmit the object data items (Step 105).

(Data Acquisition Phase)

The control unit 30 transitions to a data acquisition phase, using thetransmission permission notification of the object data items as atrigger. Specifically, for example, the control unit 30 determines,based on the output of the detector 20, a frame (in this example, frameF4) closest to the azimuth of a current field of view V (display unit10) and requests to transmit image data of the object (in this example,the object B4) belonging to this frame (Step 106). In response to thisrequest, the portable information terminal 200 transmits the image dataof the object B4 to the control unit 30 (Step 107). The control unit 30stores the received image data of the object B4 in the memory 302 andarranges the object B4 in the frame F4 in the cylindrical coordinatesC1.

Next, the control unit 30 determines a frame (in this example, frame F3)that is the second closest to the azimuth of the field of view V next tothe frame F4 and requests to transmit the image data of the object (inthis example, object B3) belonging to the frame (Step 108). In responseto this request, the portable information terminal 200 transmits theimage data of the object B3 to the control unit 30 (Step 109). Thecontrol unit 30 stores the received image data of the object B3 in thememory 302 and arranges the object B3 in the frame F3 in the cylindricalcoordinates C1.

As described above, the control unit 30 is configured to be capable ofregistering the frame data items of the objects in the cylindricalcoordinates C1 in advance such that the acquisition priority of theobjects with the current field of view V being a reference can bedetermined, and to acquire, based on the determination result, imagedata items sequentially from the object with a high priority (closest tofield of view V).

In the case where the object is an animation image, priority settingonly needs to be performed in view of a current time and an animationframe time. For example, the control unit 30 is configured to requestthe portable information terminal 200 to collectively transmit at leastsome of all images constituting the animation image. Thus, even if theobject is the animation image, it is possible to dynamically deal withsuch a case by cashing a necessary number of images (e.g., images forone second) in view of the frame rate.

For constructing the system as described above, it is necessary toincrease the capacity of the memory 302 that retains the object dataitems. However, by retaining preferentially the object data items with ahigh necessity and dynamically carrying out a process of discarding dataitems with a low necessity, suitable object display can be realized evenif the data items of all the objects cannot be retained. Note that thediscarded data items only need to be acquired again if necessary.

That is, the control unit 30 may be configured to regularly evaluate,with respect to all the objects stored in the memory 302, distancesbetween the coordinate positions thereof and the display region of thefield of view V and remove, from the memory 302, the object at thecoordinate position furthest from the display region of the field ofview V. Specifically, based on a relative position relationship betweeneach of all the objects in the cylindrical coordinates C1 and thecurrent azimuth of the field of view V, the priorities of all theobjects are evaluated and the object data with a low priority isremoved. With this, a storage area of the object data close to the fieldof view V can be ensured.

A method of evaluating a priority is not particularly limited. Forexample, the priority can be evaluated based on the number of pixelsbetween the center position of the field of view V in the cylindricalcoordinates C1 and the center position of the object. Further, in thecase of the animation image, the evaluation value may be multiplied by acoefficient based on the reproduction time.

[Operations of HMD]

Next, an example of operations of an HMD system including the thusconfigured HMD 100 according to this embodiment will be described.

FIG. 14 is a flowchart for describing an outline of the operations ofthe HMD system according to this embodiment.

First, using the position information acquisition unit 207 of theportable information terminal 200, the current position of the user U(display unit 10) is measured (Step 201). The position information ofthe display unit 10 is transmitted to the server N. Then, the portableinformation terminal 200 acquires, from the server N, object datarelating to a predetermined target present in the real space around theuser U (Step 202).

Next, the portable information terminal 200 can issue a notificationthat the preparation for transmitting the object data to the controlunit 30 is complete. The control unit 30 (in this example, coordinatesetting unit 311) sets the height (H) and the radius (R) of thecylindrical coordinates C0 serving as the world coordinate system inaccordance with the kind of object data and the like (Step 203).

In this case, if the region-limiting function in accordance with theheight (Hv) of the field of view V provided by the display unit 10 isenabled, the coordinate setting unit 311 sets the world coordinatesystem to the cylindrical coordinates C1 shown in FIG. 12A, for example.

Next, the control unit 30 detects the azimuth of the field of view Vbased on the output of the detector 20 (Step 204). The control unit 30acquires the object data from the portable information terminal 200 andstores it in the memory 302 (Step 205).

FIG. 15 is a flowchart showing an example of a reception process of theobject data by the control unit 30.

After receiving a transmission permission check of the object data fromthe portable information terminal 200 (Step 301), the control unit 30determines whether or not the frame registration of all the objects iscomplete (Step 302). That is because the coordinate position of theobject is not fixed unless the frame registration of all the objects isnot complete and the evaluation of the object priority is impossible.The process is terminated if the frame registration is not complete, andthe registration process of the above-mentioned incomplete frame isexecuted.

Otherwise, if the frame registration of all the objects is complete, thepresence and absence of an object not received and the capacity of thememory 302 is checked (Step 303). If there is an unregistered object andthe memory capacity are sufficient, the unregistered object is receivedand stored in the memory 302 (Step 304).

Note that the control unit 30 regularly evaluates the priority of theobject in the memory 302 and removes one with a low evaluation value ifnecessary.

If any object data item is present in the corresponding region of thefield of view V in the cylindrical coordinates C0, the control unit 30displays (draws) this object at the corresponding position in the fieldof view V via the display unit 10 (Step 206). In displaying the objectin the field of view V, any of the above-mentioned object display fixingfunctions may be applied.

FIG. 16 is a flowchart showing an example of a drawing procedure of theobjects in the field of view V by the control unit 30.

The control unit 30 calculates the azimuth of the current field of viewV based on the output of the detector 20 (Step 401). The azimuth of thefield of view V is converted into the world coordinate system (θ, h) andwhich position in the cylindrical coordinates C0 it corresponds to ismonitored.

Next, the control unit 30 determines whether or not there is anunscanned object among all the objects stored in the memory 302 (Step402). The scan is performed on all the objects stored in the memory 302once per screen update.

If there is an unscanned object, whether or not this object is theobject of the world coordinate system is determined (Step 403) and thisobject is drawn in the field of view V in the case of “No” (Step 404).

Otherwise, if the determination is “Yes” in Step 403, then, whether ornot any of the object display fixing functions (e.g., first grabfunction) is applied to that object is determined (Step 405). If thatfunction is applied, that object is fixedly displayed in the field ofview V at a time when an intended condition is satisfied (Step 406).Otherwise, if any display-fixing function is not applied, that object isdrawn in the field of view V at a time when the object position iscaught in the field of view V (Step 407).

Hereinafter, the above-mentioned processes are repeated. With this, itbecomes possible to provide the latest object corresponding to thecurrent position of the user U via the display unit 10 to the user U.

APPLICATION EXAMPLES

Hereinafter, application examples of the HMD 100 according to thisembodiment will be described.

Application Example 1

If the display mode of the images provided through the field of view Vis the same, in some cases, it is not useful for the user depending onthe attribute (kind) of information displayed by it. Therefore, thedisplay control unit 314 is configured to acquire the information on therelative position between the display unit 10 and the targets A1 to A4and control the display mode of the images displayed in the field ofview V in accordance with a change in relative position.

FIG. 17 shows a display mode of an object (image) B21 relating to atarget T21. The target T21 is, for example, a coffee shop in a town. Theobject B21 shows that a particular coupon is αvailable as informationrelating to the target T21. There is a case where it is desirable todisplay such an object including character information or the like at aconstant size irrespective of the distance between the user and theobject.

In this example, the display control unit 314 acquires, via the detector20 and the portable information terminal 30, information on a relativedistance between the display unit 10 and the target T21 as theinformation on the relative position between the display unit 10 and thetarget T21. Then, the display control unit 314 is configured to change,in accordance with a change in relative distance, the position of theobject B21 displayed in the field of view V.

With this, also if the target T21 is distant from the user, it ispossible for the user to view the information relating to the target T21and know the position of the target T21 based on the indication positionof the object B21. In addition, as the distance between the user and thetarget T21 becomes shorter, the size and the position of the target T21in the field of view V also are changed. At this time, the displayposition of the object B21 is also changed, and hence it is possible forthe user to easily identify the position of the target T21.

The change of the display position of the object B21 is executed, forexample, when the distance between the user and the target is changed bya predetermined value or more. For example, when the relative distancebetween the user and the target is equal to or larger than apredetermined value (e.g., 10 m or more) is changed, re-display(re-rendering) of the object B21 to the field of view V is executed.With this, in comparison with a case where re-display of the object isconstantly executed at predetermined short time intervals, it ispossible to realize a reduction of the load of processes such ascalculation at the control unit 30.

On the other hand, FIG. 18 shows a change in display mode of an object(image) B22 relating to a target T2². In this example, the displaycontrol unit 314 is configured to change, in accordance with a change inrelative distance between the display unit 10 and the target T22, theposition and the size of the object B21 displayed in the field of viewV.

In this example, several display levels are set depending on thedistance between the user and the target. FIG. 18 shows a state in whichthe same object B22 is moved to the right while being gradually enlargedas the user approaches the target T22. The object previously displayedis hidden when the subsequent object is displayed. The change in displaylevel may include a phase in which the display position or the size ofthe object is changed.

According to such a display mode of the objects, information relating tothe target present near the user can be displayed in the field of view Vin preference to information relating to the target present at aposition spaced apart from the user. Note that, as for the priority ofthe objects displayed in the field of view V, display information ofother attributes (destination information, update information,place-name information) may be set as the reference parameter other thanthe distance information.

FIG. 19 shows a display mode of an object (image) B23 relating to thetarget T23. In this example, the object B23 is a three-dimensional imageand the display control unit 314 acquires, via the detector 20 and theportable information terminal 30, as the information on the relativeposition between the display unit 10 and the target T23, information onthe angular position of the display unit 10 with the target T23 being acenter. Then, the display control unit 314 is configured tothree-dimensionally change, in accordance with a change in angularposition, the orientation of the object B21 displayed in the field ofview V.

According to such a display mode of the objects, for example, by theuser walking around the target T23, the object B23 rotating in ahorizontal plane can be displayed. For example, if the target T23 is ahistoric spot or site, the state of that time may be three-dimensionallydrawn as the object B23. If the target T23 is a site for a building, abuilding planned to be constructed may be drawn as the object B23.

In this case, the memory 302 is configured to store a plurality ofimages relating to the predetermined target and the display control unit314 is configured to select an image, which should be displayed in thefield of view V, from among the plurality of images according to a useroperation.

For example, as shown in FIG. 20 , if a target T24 is a castle site in acertain tourist area, an object B24 including information on the castlesite in the field of view V. The object B24 displays the presence of animage, in which the state of the castle of that time is reproduced, in apredetermined manner. Then, according to an operation of the inputoperation unit 305 by the user, the object B24 is switched to an objectB24 a in which the state of the castle of that time is reproduced asshown in FIG. 21 . Alternatively, according to the above-mentionedoperation, the object B24 is switched to an object B24 b in which thestate or position of a castle in the past before that time isreproduced.

Note that the image data of the objects B24 a and B24 b is acquired byinstalling a tourist area application that can be downloaded from aserver of a community, for example, into the portable informationterminal 200.

Application Example 2

If the plurality of images are displayed in the field of view V, thereis a case where the visibility of the image is rather deteriorated andinformation cannot be appropriately presented to the user. Therefore,the display control unit 314 is configured to extract the imageincluding information meeting at least one display condition set by theuser from the memory 302 (storage unit) and selectively display theextracted image in the field of view V.

In this example, filtering is performed using an attribute parameter ofthe objects and those projected (drawn) to the cylindrical coordinatesC0 or those not projected (drawn) to the cylindrical coordinates C0 aredetermined. As an attribute parameter of the objects, for example, thefollowing is exemplified.

-   -   (1) distance from user (examples: objects within 100 m)    -   (2) degree of importance (examples: destination, current        locations of friends, traffic congestion information)    -   (3) category (examples: tourist spot, convenience store)    -   (4) update time (examples: bulletin board information)    -   (5) history time (examples: historic site picked up with time        information being reference)

As a method of using filtering, for example, a filtering condition isregistered on a scenario mode prepared in advance and only objectsmeeting this filtering condition can be displayed in the field of viewV. The scenario mode and the filtering condition are input by the userinto the portable information terminal 200, for example.

As an example of the scenario mode, the following is exemplified.

-   -   (a) tourist mode (examples: display tourist spots within 1 km        radius)    -   (b) historic site search mode (examples: display historic site        of the Edo era within 10 km radius)    -   (c) new information display mode (examples: display 20 items at        new update date and time within 10 km radius)    -   (d) friend search mode (examples: display five friends near        user)

For example, in the case of (a) above, the attribute parameters (1) and(3) are input as the filtering condition. Similarly, (1) and (5) in thecase of (b) above, (1) and (4) in the case of (c) above, and (1) and (2)in the case of (d) above are each input as the filtering condition.

FIG. 23 is a flowchart of processes executed at the control unit 30(display control unit 314).

The control unit 30 extracts, from the objects stored in the memory 302,an object meeting the input filtering condition (display condition) andprojects it to the cylindrical coordinates C0 (Steps 501 and 502).Subsequently, the control unit 30 calculates a movement distance of theuser from the previous object projection time and re-projects the objectto the cylindrical coordinates C0 if it is equal to or larger than apredetermined value (e.g., 10 m or more) (Steps 503, 501, and 502). Theabove-mentioned processes are repeated until this scenario mode isterminated.

The re-projection of the objects includes a change in position or sizeof the same object, projection of a new object, and the like.

Display Control Example 1

FIG. 24 shows a display example of the object when a car navigationapplication is set as the scenario mode, for example. Here, as thefiltering condition, an example in which the position of a friend inanother car, destination information, and traffic signal names are inputwill be described.

Various objects relating to the target as viewed from a car driven bythe user are displayed in the field of view V. The target includes afriend's car, traffic signals, and a destination. As objects relatingthereto, position information of the friend's car (B251), anintersection name (signal name) (B252), and position and distanceinformation of the destination (B253) are displayed. The object B251 isdisplayed based on an ID or the like of an HMD that the friend wears,which is input into the portable information terminal 200 of the user.

An intersection (traffic signal) present within 100 m distance from theuser, for example, as a distance condition is set as a target of theobject B252 relating to the intersection name. On the other hand,regarding the objects B251 and B253 relating to the friend's car and thedestination, the distance condition does not need to be applied becauseit is important information.

The control unit 30 displays the objects B251 to B253 in the field ofview V based on the position information of the user. The control unit30 monitors the movement distance of the user after the objects B251 toB253 are displayed. If it becomes equal to or larger than apredetermined distance (e.g., 10 m), in order to change the position andsize of the objects B251 to B253 or display the object including thenext intersection name, the objects in the field of view V are updated.Such a display control is repeatedly executed until the user arrives atthe destination.

(Display Control Example 2) On the other hand, if many objects aredisplayed in the field of view V or the objects are displayed in anoverlapping manner, there is a case where it is difficult to identify orview the objects in a manner useful for the user. Therefore, the controlunit 30 (display control unit 314) may be configured to alternatelydisplay, if the image that should be displayed in the field of view Vincludes a plurality of images, the plurality of images.

For example, as shown in FIGS. 25A and 25B, the object B252 showing theintersection name and the objects B251 and B253 showing the friend's carinformation and the destination information may be alternately displayedfor each predetermined time. With this, the visibility anddiscriminability of the objects in the field of view V can be increased.

If each display position is deviated and displayed such that the objectsdo not overlap with each other, there is a case where it is difficult toidentify the correspondence between the objects and the targets.According to this example, the visibility and the discriminability ofthe objects are ensured by offsetting the display timing of each objectin a time direction.

Alternatively, the group of the objects displayed at the same time maybe classified for each attribute parameter. With this, object listingproperties are ensured, and hence information superior for the user canbe checked at one view.

In addition, in accordance with the number of objects in the field ofview V and the overlapping amount, a group of displayed objects or agroup of alternately displayed objects may be determined. For example,the intersection name and the building name may be displayed at the sametime in a non-crowded place and the intersection name and the buildingname may be displayed with a time lag in a crowded place.

Second Embodiment

Next, a second embodiment of the present technology will be described.Hereinafter, configurations different from those of the first embodimentwill be mainly described and descriptions of the same configurations asthose of the embodiment will be omitted or simplified.

A head-mounted display according to this embodiment includes a displayunit that is configured to be mountable on a head of a user and iscapable of providing the user with a field of view of a real space, adetector that detects an azimuth of the display unit, and a displaycontrol unit that displays an image in the field of view based on anoutput of the detector.

The display control unit moves the image in the field of view inaccordance with a change in azimuth when the azimuth is changed by afirst predetermined angle or more.

The display control unit fixes a display position of the image in thefield of view when a change in azimuth is smaller than the firstpredetermined angle.

The display unit and the detector correspond to the display unit 10 andthe detector 20 described in the first embodiment, respectively. Thedisplay control unit corresponds to the display control unit 314 havingthe object display fixing function ((1) introduction of non-strictattribute) described in the first embodiment.

That is, the head-mounted display according to this embodiment isapplicable to another arbitrary coordinate system in which the worldcoordinates are not limited to the cylindrical coordinates. Also in thisembodiment, the same actions and effects as those in the firstembodiment can be obtained. That is, it is possible to easily keep theobject in the field of view, and hence it is possible to regulate themovement of the object, which results from a spontaneous change inattitude of the user, and to enhance the visibility of the object.

Note that, also in this embodiment, at least one of the region-limitingfunction and the image management function may be provided as in thefirst embodiment.

Third Embodiment

Next, a third embodiment of the present technology will be described.Hereinafter, configurations different from those of the first embodimentwill be mainly described and descriptions of the same configurations asthose of the embodiment will be omitted or simplified.

A head-mounted display according to this embodiment includes a displayunit that is configured to be mountable on a head of a user and iscapable of providing the user with a field of view of a real space, adetector that detects an azimuth of the display unit, and a displaycontrol unit that displays the image in the field of view based on anoutput of the detector.

The display control unit moves the image to a predetermined position inthe field of view when a change in output of the detector is equal to orsmaller than a predetermined value over a predetermined time. Otherwise,when the display control unit detects an input of a predetermined signalgenerated according to a user operation, the image is moved to apredetermined position in the field of view.

The display unit and the detector correspond to the display unit 10 andthe detector 20 described in the first embodiment, respectively. Thedisplay control unit corresponds to the display control unit 314 havingthe object display fixing function ((2) first grab function or (3)second grab function) described in the first embodiment.

That is, the head-mounted display according to this embodiment isapplicable to another coordinate system whose world coordinates are notlimited to the cylindrical coordinates. Also in this embodiment, theactions and effects as those in the first embodiment can be provided.That is, it is possible to easily keep the object in the field of view,and hence it is possible to regulate the movement of the object, whichresults from an unintended change in attitude of the user, and toenhance the visibility of the object.

Note that, also in this embodiment, at least one of the region-limitingfunction and the image management function may be provided as in thefirst embodiment.

Fourth Embodiment

Next, a fourth embodiment of the present technology will be described.Hereinafter, configurations different from those of the first embodimentwill be mainly described and descriptions of the same configurations asthose of the embodiment will be omitted or simplified.

A head-mounted display according to this embodiment includes a displayunit that is configured to be mountable on a head of a user and iscapable of providing the user with a field of view of a real space, adetector that detects an azimuth of the display unit, and a displaycontrol unit that displays the image in the field of view based on anoutput of the detector.

In a state in which the image is displayed at a predetermined positionin the field of view, when a change in output of the detector is equalto or higher than a predetermined frequency, the display control unitcancels frequency components of the output of the detector, which areequal to or higher than the predetermined frequency.

The display unit and the detector correspond to the display unit 10 andthe detector 20 described in the first embodiment, respectively. Thedisplay control unit corresponds to the display control unit 314 havingthe object display fixing function ((4) image stabilization function)described in the first embodiment.

That is, the head-mounted display according to this embodiment isapplicable to another arbitrary coordinate system whose worldcoordinates are not limited to the cylindrical coordinates. Also in thisembodiment, it is possible to acquire the same actions and effects asthose in the above-mentioned first embodiment. That is, it is possibleto ensure the visibility of the image without receiving the influence ofa slight shake of the face of the user.

Note that, also in this embodiment, at least one of the region-limitingfunction and the image management function may be provided as in thefirst embodiment.

Fifth Embodiment

Subsequently, a fifth embodiment of the present technology will bedescribed. Hereinafter, configurations different from those of the firstembodiment will be mainly described and descriptions of the sameconfigurations as those of the embodiment will be omitted or simplified.

A head-mounted display according to this embodiment includes a displayunit, a detector, and a control unit. The display unit is configured tobe mountable on the head of the user and be capable of providing theuser with a field of view of a real space. The detector detects anazimuth around at least one axis of the display unit. The first controlunit includes a storage unit and a display control unit. The storageunit stores images including information relating to a predeterminedtarget present in the field of view with the images being madecorresponding to three-dimensional coordinates surrounding the displayunit. The display control unit is configured to display, based on anoutput of the detector, an image in the three-dimensional coordinates,which corresponds to an azimuth, in the field of view.

The display unit and the detector respectively correspond to the displayunit 10 and the detector 20 that are described in the first embodiment.The storage unit corresponds to the memory 302 described in the firstembodiment. The display control unit corresponds to the display controlunit 314 described in the first embodiment.

That is, the head-mounted display according to this embodiment isapplicable to another arbitrary coordinate system in which the worldcoordinates are not limited to the cylindrical coordinates. Also in thisembodiment, the same actions and effects as those in the firstembodiment can be obtained.

In this embodiment, the display control unit may be configured toconvert a predetermined image stored in the storage unit into acoordinate value falling within the display area of the field of viewalong the direction of the one axis and display it in the field of view.With this, a drawing control of the objects following the height of thefield of view V can be performed and the same actions and effects asthose of the region limiting function described in the first embodimentcan be obtained.

For example, on the display mode on which the region limiting functionis enabled, as shown in FIG. 26 , if the height coordinates of theobjects B11 and B12 in the cylindrical coordinates exceed the displayarea of the field of view V, the user U cannot display the objects B11and B12 in the field of view V by changing the attitude in thehorizontal plane in the field of view V.

On the other hand, in the case of the image control of the objectsfollowing the height of the field of view V, the height coordinates ofthe objects B11 and B12 are also limited following limitation of theregion of the field of view V in the height direction. As a result, asshown in FIG. 27A, the height coordinates of the objects B11 and B12 arechanged to fall within the display region of the field of view V and itbecomes possible to display the objects B11 and B12 corresponding to theazimuths in the field of view V only by the attitude of the user U beingchanged in the horizontal plane.

Further, as shown in FIGS. 27B and 27C, even when the field of view V ischanged in the height direction, the height coordinates of the objectsB11 and B12 are also changed following the height coordinates of thefield of view V. Also when the user looks around looking at an upper orlower area, it becomes possible to view objects B11 and B12.

As described above, the objects following the height of the field ofview V may be all objects in the cylindrical coordinates C0 or may bepart of the objects. For example, such selection of the objects may beperformed by the user or an object showing important information may bepreferentially selected.

Although the embodiments of the present technology have been described,the present technology is not limited only to the above-mentionedembodiments and various changes can be added without departing from thegist of the present technology, of course.

For example, although the example in which the present technology isapplied to the HMD has been described in each of the above-mentionedembodiments, the present technology is applicable also to a head updisplay (HUD) installed into, for example, a compartment of a vehicle ora cockpit of an airplane as the image display apparatus other than theHMD.

Further, although the application example to the see-through-type HMDhas been described in each of the above-mentioned embodiments, thepresent technology is applicable also to a non-see-through-type HMD. Inthis case, predetermined objects according to the present technologyonly need to be displayed in an external field of view captured by acamera mounted on the display unit.

In addition, although the HMD 100 is configured to display an objectincluding information relating to a predetermined target present in thereal space in the field of view V in each of the above-mentionedembodiments, it is not limited thereto and a destination guide or thelike may be displayed in the field of view V based on a current positionor a direction of movement of the user U.

Note that the present technology may also take the followingconfigurations.

-   -   (1) A head-mounted display, including:        -   a display unit that is configured to be mountable on a head            of a user and is capable of providing the user with a field            of view of a real space;        -   a detector that detects an azimuth of the display unit            around at least one axis; and        -   a first control unit including            -   a region limiter that is capable of limiting a display                region of the field of view along a direction of the one                axis in three-dimensional coordinates surrounding the                display unit,            -   a storage unit that stores images including information                relating to a predetermined target present in the field                of view with the images being made corresponding to the                three-dimensional coordinates, and            -   a display control unit configured to display, based on                an output of the detector, an image in the                three-dimensional coordinates, which corresponds to the                azimuth, in the field of view.    -   (2) The head-mounted display according to (1), in which        -   the display control unit acquires information on a relative            position between the display unit and the predetermined            target and controls a display mode of an image displayed in            the field of view in accordance with a change in relative            position.    -   (3) The head-mounted display according to (2), in which        -   the information on the relative position includes            information on a relative distance between the display unit            and the predetermined target, and        -   the display control unit changes, in accordance with the            change in relative distance, at least one of a position and            a size of the image displayed in the field of view.    -   (4) The head-mounted display according to (2), in which        -   the information on the relative position includes            information on an angular position of the display unit with            the predetermined target being a center, and        -   the display control unit three-dimensionally changes, in            accordance with a change in angular position, an orientation            of the image displayed in the field of view.    -   (5) The head-mounted display according to (2), in which        -   the display control unit extracts an image including            information meeting at least one display condition set by            the user from the storage unit and selectively displays the            extracted image in the field of view.    -   (6) The head-mounted display according to (5), in which        -   the display control unit alternately displays, when an image            that should be displayed in the field of view includes a            plurality of images, each of the plurality of images.    -   (7) The head-mounted display according to (5), in which        -   the storage unit stores a plurality of images relating to            the predetermined target, and        -   the display control unit selects, according to a user            operation, an image that should be displayed in the field of            view from among the plurality of images.    -   (8) The head-mounted display according to any one of (1) to (7),        in which        -   the detector detects an azimuth of the display unit around a            vertical axis, and        -   the region limiter limits a region in a height direction in            cylindrical coordinates around the vertical axis in            accordance with a region of the field of view in a vertical            direction.    -   (9) The head-mounted display according to any one of (1) to (8),        in which        -   the display control unit            -   moves, when the azimuth is changed by a first                predetermined angle or larger, the image in the field of                view in accordance with a change in azimuth, and            -   fixes a display position of the image in the field of                view when the change in azimuth is smaller than the                first predetermined angle.    -   (10) The head-mounted display according to any one of (1) to        (9), in which        -   the display control unit moves the image to a predetermined            position in the field of view when a change in output of the            detector is equal to or smaller than a predetermined value            over a predetermined time.    -   (11) The head-mounted display according to any one of (1) to        (10), in which        -   the display control unit moves the image to a predetermined            position in the field of view when an input of a            predetermined signal generated according to an operation of            the user is detected.    -   (12) The head-mounted display according to any one of (1) to        (11), in which        -   the display control unit cancels, when a change in output of            the detector is equal to or higher than a predetermined            frequency in a state in which the image is displayed at a            predetermined position in the field of view, a frequency            component of the output of the detector, which is equal to            or higher than the predetermined frequency.    -   (13) The head-mounted display according to any one of (1) to        (12), in which        -   the first control unit limits, when an input of a            predetermined signal generated according to an operation of            the user is detected, a region in the height direction in            the three-dimensional coordinates in accordance with a            region of the field of view in the direction of the one            axis, and adjusts all the images displayed in the field of            view to the same height in the field of view.    -   (14) The head-mounted display according to any one of (1) to        (13), in which        -   the image includes an animation image.    -   (15) The head-mounted display according to any one of (1) to        (14), further including        -   a second control unit including an image acquisition unit            that acquires a plurality of images stored in the storage            unit.    -   (16) The head-mounted display according to any one of (15), in        which        -   the first control unit requests the second control unit to            transmit one or more images selected from among the            plurality of images.    -   (17) The head-mounted display according to (15) or (16), in        which        -   the first control unit requests the second control unit to            preferentially transmit an image made corresponding to a            coordinate position closer to the display region of the            field of view in the three-dimensional coordinates.    -   (18) The head-mounted display according to any one of (15) to        (17), in which        -   the second control unit further includes a position            information acquisition unit that is capable of acquiring            position information of the display unit, and        -   the image acquisition unit acquires an image corresponding            to the position information that can be transmitted to the            first control unit.

DESCRIPTION OF SYMBOLS

-   -   10 display unit    -   11R, 11L display surface    -   12R, 12L image generator    -   20 detector    -   30 control unit    -   100 head-mounted display (HMD)    -   200 portable information terminal    -   311 coordinate setting unit    -   312 image management unit    -   313 coordinate determination unit    -   314 display control unit    -   A1 to A4 target    -   B, B1 to B4 object    -   C0, C1 cylindrical coordinate (world coordinate)    -   V field of view    -   U user

1. An information processing apparatus comprising: a display device,wherein the display device is configured to provide a user with a fieldof view of a real space; and circuitry configured to detect an attitudeof the display device around at least one axis, and initiate display ofa virtual object by the display device in the field of view, wherein, ina first mode, the display device displays the virtual object at a fixedposition in a first coordinate system, wherein, in a second mode, thedisplay device displays the virtual object at a fixed position in asecond coordinate system and a position that changes in the firstcoordinate system based on a change of the attitude of the displaydevice, and wherein the circuitry is further configured to switch thedisplay of the virtual object by the display device between the firstmode and the second mode based on an input operation of the user.
 2. Theinformation processing apparatus according to claim 1, wherein thecircuitry is further configured to limit a height coordinate of thevirtual object within the display region in the field of view along theone axis in three-dimensional coordinates surrounding the displaydevice.
 3. The information processing apparatus according to claim 1,wherein the first coordinate system is a world coordinate system and thesecond coordinate system is a cylindrical coordinate system.
 4. Theinformation processing apparatus according to claim 1, wherein a heightof the position of the virtual object changes so that the virtual objectis disposed within a display region in the second coordinate system. 5.The information processing apparatus according to claim 4, wherein thevirtual object disposed over the display region in the first coordinatesystem goes down to the display region, and another virtual objectdisposed under the display region in the first coordinate system goes upto the display region.
 6. The information processing apparatus accordingto claim 4, wherein a height of a position of another virtual objectdoes not change based on a mode change between the first mode and thesecond mode.
 7. The information processing apparatus according to claim4, wherein whether heights of positions of the virtual object andanother virtual object change is determined based on the input operationof the user.
 8. The information processing apparatus according to claim1, wherein the first coordinate system is a real space coordinatesystem.
 9. A head-mounted display comprising: a display deviceconfigured to be mountable on a head of a user, wherein the displaydevice is configured to provide the user with a field of view of a realspace; and circuitry configured to detect an attitude of the displaydevice around at least one axis, and initiate display of a virtualobject by the display device in the field of view, wherein, in a firstmode, the display device displays the virtual object at a fixed positionin a first coordinate system, wherein, in a second mode, the displaydevice displays the virtual object at a fixed position in a secondcoordinate system and a position that changes in the first coordinatesystem based on a change of the attitude of the display device, andwherein the circuitry is further configured to switch the display of thevirtual object by the display device between the first mode and thesecond mode based on an input operation of the user.
 10. Thehead-mounted display according to claim 9, wherein the circuitry isfurther configured to limit a display region in the field of view alonga direction of the one axis in three-dimensional coordinates surroundingthe display device.
 11. The head-mounted display apparatus according toclaim 9, wherein the first coordinate system is a world coordinatesystem and the second coordinate system is a cylindrical coordinatesystem.
 12. The head-mounted display apparatus according to claim 9,wherein a height of the position of the virtual object changes so thatthe virtual object is disposed within a display region in the secondcoordinate system.
 13. The head-mounted display apparatus according toclaim 12, wherein the virtual object disposed over the display region inthe first coordinate system goes down to the display region, and anothervirtual object disposed under the display region in the first coordinatesystem goes up to the display region.
 14. The head-mounted displayapparatus according to claim 12, wherein a height of a position ofanother virtual object does not change based on a mode change betweenthe first mode and the second mode.
 15. The head-mounted displayapparatus according to claim 14, wherein whether heights of positions ofthe virtual object and another virtual object change is determined basedon the input operation of the user.
 16. The head-mounted displayapparatus according to claim 9, wherein the first coordinate system is areal space coordinate system.
 17. A method, executed by at least oneprocessor, the method comprising: providing a user with a field of viewof a real space via a display device; detecting an attitude of thedisplay device around at least one axis; and displaying a virtual objectin the field of view under the control of a display control unitimplemented via the at least one processor, wherein, in a first mode,the display control unit displays the virtual object at a fixed positionin a first coordinate system, wherein, in a second mode, the displaycontrol unit displays the virtual object at a fixed position in a secondcoordinate system and a position that changes in the first coordinatesystem based on a change of the attitude of the display device, andwherein the display of the virtual object under the control of thedisplay control unit switches between the first mode and the second modebased on an input operation of the user.
 18. The method according toclaim 17, wherein the method further comprises: using a region limiterimplemented via the at least one processor to limit a display region inthe field of view along a direction of the one axis in three-dimensionalcoordinates surrounding the display device.
 19. The method according toclaim 17, wherein the first coordinate system is a world coordinatesystem and the second coordinate system is a cylindrical coordinatesystem.
 20. The method according to claim 17, wherein a height of theposition of the virtual object changes so that the virtual object isdisposed within a display region in the second coordinate system. 21.The method according to claim 20, wherein the virtual object disposedover the display region in the first coordinate goes down to the displayregion, and another virtual object disposed under the display region inthe first coordinate system goes up to the display region.
 22. Themethod according to claim 20, wherein a height of a position of anothervirtual object does not change based on a mode change between the firstmode and the second mode.
 23. The method according to claim 22, whereinwhether heights of positions of the virtual object and another virtualobject change is determined based on the input operation of the user.24. The method according to claim 17, wherein the first coordinatesystem is a real space coordinate system.